Collector comprising rings skewed to beam and increasing in diameter along beam



March 23, 1965 G. WENDT 3,175,120

COLLECTOR COMPRISING RINGS SKEWED TO BEAM AND INCREASING IN DIAMETER ALONG BEAM Filed. Feb. 6, 1961 3 Sheets-Sheet 1 BY I M ATTO RNEYS March 23, 1965 G DT 3,175,120

W V COLLECTOR COMPRISING RINGS SKEWED TO BEAM AND INCREASING IN DIAMETER ALONG BEAM Filed Feb. 6, 1961 5 Sheets-Sheet 2 INVENTOR {5.WENDT av M ATTORNEY March 23, 1965 G. WENDT 3,175,120

COLLECTOR COMPR NG RINGS SKEWED TO BEAM AND INCREASING N DIAMETER ALONG BEAM Filed Feb. 6, 1961 3 Sheets-Sheet 3 INVENTOR G.WENDT BY M 7 ATTORNEYS United States Patent ()fiiice 3,l75,l20 Patented Mar. 23, 1955 9 Claims. (a. 315-5.38)

The present invention relates to electron discharge devices of the velocity modulation type, and more particularly relates to the collector electrode structure for the electrons forming part of such electronic tubes.

It is known that the operation of the tubes of this type, which include in particular klystrons and traveling wave tubes, is based on an exchange of energy between the electron beam and a U.H.F. electromagnetic wave, and that, consequently, the output power of such a tube is a function of the energy of the electron beam thereof. In order to obtain relatively high output powers, it is therefore necessary to utilize electron beams of very great intensity which are subjected to very high accelerating voltages.

Since the cross section of the beam perpendicular thereto has, in practice, a rather limited surface, relatively great intensities of electron beams necessitate very great densities of electron flux. However, after passage through the space in which takes place the interaction between the electron beam and the high frequency wave, the electrons will, as is known, impinge on the collector electrode, generally constituted by a cylinder or by a hollow metallic cone of which the capacity of thermal dissipation has a well-defined maximum value, for example, from 150 to 1000 Watts per centimeter square which cannot be exceeded.

Under these conditions, a suitable dissipation of the heat On the collector electrodes of the tubes of high power can actually be realized only if these tubes function at pulsed operation in which the periods of operation are very brief and are separated by intervals or" rest which are relatively long. These same prior art tubes, in contradistinction thereto, are not suitable for use in a system of continuous, i.e, non-pulsed, uninterrupted operation in which, for the same nominal power, the quantity of heat to be dissipated becomes 100 to 1000 times greater, as the collectors in their actual form known in the prior art are not suitable to assure such dissipations.

It is known, on the other hand, that secondary electron emissions take place generally, within a certain measure, under the influence of shocks or collisions of electrons impinging on the surface of the collector and that a portion of the secondary electrons thus produced penetrate into the interior space of the tube. Moreover, in the case of tubes provided with an electron beam in which the electrons, prior to reaching the collector, are subjected to a decelerating field, the vast majority of the electrons thereof have well an energy sufiicient to permit the same to reach the walls of the collector and to be absorbed thereat; however, a certain number among them, namely those of relatively weak energy, are subject to reflections and return toward the interior of the tube. The penetration into the interior space of the tube on the part of the electrons arriving in a direction inverse to that of the electron beam, however, constitutes a cause of disturbance in the proper operation of the tube which is the more annoying the greater the power of the tube.

The present invention has for its object a new collector structure and new dispositions which permit to eliminate in the tubes under consideration the shortcomings mentioned hereinabove. Consequently, the present invention aims at the realization of electron tubes of the velocity modulation type, such as klystrons or traveling wave tubes, of high or very high power, exceeding 100 kilowatts or attaining 1 megawatt or even more, which can be operated not only as pulsed tubes but also under continuous operation. Another object of the present invention essentially consists in providing an electron collector which renders practically impossible the escape from its enclosure of reflected electrons and of those due to secondary emissions.

Accordingly, it is an object of the present invention to provide an electron tube of the type mentioned hereinabove which effectively eliminates the inadequacies and shortcomings of the prior art devices.

It is another object of the present invention to provide an electron discharge device providing an energy interchange between an electron beam and an electromagnetic wave which may be operated at very high power outputs.

Still another object of the present invention resides in the provision of an electron discharge device of the type mentioned hereinabove in which the collector electrode is so constructed and arranged as to permit ready dissipation of the relatively large amount of heat generated therein as a result of operation thereof at extremely high power levels.

A further object of the present invention resides in the provision of an electrode arrangement for electron discharge devices of the type mentioned hereinabove in which any possible impairment of the proper and undisturbed operation of the tube at extremely high power levels is effectively precluded by controlling, in a novel manner, any reflected electrons, reflected from the collector electrode and/ or the behavior of secondary emission electrons.

A further object of the present invention resides in the provision of an electron discharge device of the type described hereinabove which lends itself readily to highpower continuous operation.

These and other objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein FIGURE 1 is a longitudinal axial cross sectional view of a first embodiment of an electron discharge device of the klystron type provided with a collector structure in accordance with the present invention;

FIGURE 2 is a longitudinal, axial cross sectional view of the tube illustrated in FIGURE 1 taken in a plane perpendicular to that of FIGURE 1;

FIGURE 3 is a perspective view of the collector structure of FIGURES 1 and 2;

FIGURE 4 is an end elevational view illustrating one embodiment of a collector structure for use in the embodiment of FIGURES l, 2 and 3;

FIGURE 5 is a longitudinal cross sectional view through a modified embodiment of a collector structure in accordance with the present invention, and

FIGURE 6 is an enlarged, partial cross sectional view through a still further modified embodiment of a collector construction in accordance with the present invention.

According to the present invention, the collector of a tube provided with an electron beam forms a metallic enclosure on the inside of which are established a magnetic field of decreasing intensity and an electrostatic decelerating field inclined with respect to the magnetic field, these two fields being, on the other hand, inclined along different planes with respect to the direction of propagation of the beam of electron stream on the inside of the tube.

is also the anode potential of the tube.

According to one preferred embodiment of the present invention, the Collector structure forms a cone constituted by a series of metallic rings of increasing diameter in the direction of propagation of the electron beam and carried at decreasing voltages in the same direction with respect to the potential of the first one thereof, the axis of the cone subtending an acute angle with respect to the axis of the tube, and all of the rings or annular members being inclined with respect to the plane containing simultaneously the axis of the tube and the axis of the cone, while means are provided, on the other hand, to produce a static magnetic field, directed at least approximately along the axis of the cone, with an intensity that decreases in the direction of propagation of the electron beam.

Even though the invention, in its general aspects, concerns all electron tubes of high power in which a strongly focused electron beam is directed toward an electron collector electrode, the present invention will be described hereinafter with reference to a klystron type tube of high power, having four cavities illustrated in FIGURES l and 2 in cross section along two orthogonal planes passing through the axis of the tube, it being understood that such description with respect to a klystron type tube is only for purposes of illustration and not intended in any Way to limit the general aspects and universal applicabilities of the present invention to any other type of electron discharge device of the general type referred to hereinabove.

Referring now to the drawing wherein like reference numerals are used throughout the various views to desig nate like parts, and more particularly to FIGURES l and 2 thereof, the tube illustrated therein includes an emissive cathode 1 providing an electron beam which traverses, on the inside of the cylindrical member 2, an interaction space composed of so-called drift spaces or tunnels, such as drift space 3, separated by resonant cavities 4.

The first one of these cavities 4, namely the one that is nearest to the cathode l, is coupled or operatively connected in any suitable manner with an input line 5 of any suitable construction whereas the last one of the cavities 4, namely the one farthest removed from the cathode 1, is operatively connected with an output Wave guide 6 of any suitable construction, the input and output of the U.H.F. electromagnetic energy taking place respectively in the direction of the arrows 7 and 8.

An electron collector, according to the present invention, is located at the end of the body or member 2 of the tube adjacent the output cavity 4 thereof. The collector structure in accordance with the present invention, which is illustrated in one embodiment thereof in FIGURES 1 and 2 in cross sectional view and in FIG- URE 3 in perspective view in which some parts are broken away for claritys sake, comprises a series of metallic rings or annular members 9 of increasing diameter in the direction of propagation of the electrons.

The rings or annular members 9 are so disposed that the axis 11 thereof, that is, the line passing through the centers thereof, subtends or forms an acute angle with the axis of the tube (FIGURE 2), all of the rings or annular members 9 being, on the other hand, inclined with respect to the plane containing the two axes 10 and 11. A metallic plate 12 terminates the conical space formed by the rings 9.

The plate 12 is carried at a voltage essentially equal to that of the cathode 1 by means of a source of voltage 13 which places the cathode 1 at a strongly negative voltage with respect to the potential of the body 2 which On the other hand, according to the present invention, successive rings 9 are carried at intermediate potentials between the anode potential and the potential of the plate 12, these potentials having decreasing values from the first ring adjacent the high frequency output cavity which has tie highest potential, in the neighborhood of that of the anode potential,

i to the last ring adjacent the plate 12 which has the lowest potential, in the neighborhood of that of the cathode 1.

FIGURE 2 illustrates more clearly how the successive rings 9 are connected between the and the terminal of the direct current voltage source 13.

The collector which includes the rings 9 and the terminal plate 12 is enclosed within an evacuated enclosure or vessel 14 of conical shape and made of insulating material or of non-magnetic metal such as, for example, copper, as indicated in FIGURES 1 and 2.

Coils 15 surround the body of the tube 2 in order to provide, according to any well known technique, a magnetic focusing field directed along the aXis of the tube.

According to the present invention, coils or windings 15, connected in series and fed by direct current from a suitable direct current source (not illustrated) are disposed about the conical portion 14. The individual coils or windings 15' have decreasing numbers of turns, respectively, in the direction of propagation of the electron beam, and as all of the windings 15' connected in series are traversed by the same direct current, they produce a magnetic field of decreasing intensity in the direction of propagation of the beam, i.e., in the direction from left toward the right as viewed in FIGURES l and 2, directed essentially along the axis of the cone 14 and of the rings 9. However, it is also understood that identical coils 15 may be used and the same results could be obtained by supplying each of the windings 15' individually from a separate source of current of decreasing intensity. Thus, it is within the spirit and scope of the present invention to arrange and construct the windings 15', the interconnection with the current supply means and the mutual interconnection, if any, in any suitable manner, known in the prior art, to produce the desired result of a field having a decreasing intensity in the direction of propagation of the beam.

As the operation of a klystron type tube is sufficiently known in the art, a detailed description thereof is dispensed with herein, the more so as the present invention is concerned with the novel structure andmode of utilization of the particular collector structure in accordance with the present invention, it being understood that the particular electrode structure in accordance with the present invention is adapted to be utilized in an analogous manner with any other electron discharge device of the type mentioned hereinabove.

In effect, thanks to the described and illustrated arrangements, an axial magnetic field of decreasing intensity and an electrostatic decelerating field inclined with respect to the magnetic field are produced within the rings 9, these two fields being, on the other hand, inclined with respect to the direction of propagation of the beam within the inside of the interaction space. Under these conditions, the electrons are caused to move along helicoidal trajectories of increasing diameters on the inside of the collector structure and finish by impinging on the rings 9. The precise place of impact of each electron depends on the direction and speed with which the same enters within the collector enclosure structure, and the beam thus spreads out over all of the internal surfaces of the rings 9 and of the plate 12.

Moreover, if it happens that certain electrons, after deceleration thereof, undergo a reversal of direction within the collector enclosure, these reflected electrons can under no circumstances re-enter the region of the tube.

It may, in fact, be readily demonstrated that, by reason of the inclination of the electrostatic and magnetic fields with respect to the axis of the tube, the reflected electrons follow helicoidal trajectories about an axis strongly displaced with respect to that of the tube, this displacement effect or deviation taking place also, as is well understood, for the electrons produced by secondary emission along the internal walls of the collector.

In order to improve the capture or absorption of the electrons by the annular members or rings 9, the internal surfaces thereof may be provided with small paddles, inclined with respect to the radii of the rings 9, as indicated for example, in FIGURE 4 where these paddles are designated by reference numeral 16.

Moreover, it is, however, not absolutely necessary that the rings 9 of the collector form a regular cone about a rectilinear axis, essentially equivalent results being obtainable also if the centers of the ring 9 are disposed along a curve. It is also noted that the elements 9 of the collector need not necessarily have the shape indicated in FIGURES l to 3, another embodiment for the possible shape of these elements being illustrated in cross section in FIGURE 5 which illustrates perforated disks or washers of slight thickness.

For the latter form, there might also be provided paddles as illustrated in FIGURE 4, however, with this difference that such paddle-s would be disposed along the lateral surfaces of the disks with a certain inclination with respect to this surface.

FIGURE 6 illustrates a modified embodiment in which the body 2 of the tube is terminated by a projecting portion 17, the first ring of the collector having a portion essentially parallel to this projection. This arrangement provides a very strong inclination of the electrostatic field over the magnetic field right from the passage of the beam of electrons from the tube to the collector.

While I have shown and described several embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of many changes and modifications within the spirit and scope thereof. For example, it is obvious that for high power electron discharge devices, there exists an interest to provide the collector according to the present invention with appropriate cooling means, for example, in the form of circulation of a liquid refrigerant, however, for reasons of clarity in the drawing no such means have been indicated in the various figures thereof, the more so as the inclusion of a cooling means flowing through the collector and/ or individual collector elements is well within the skill of a person versed in the art. The collector elements, may be thereby constructed as hollow annular elements if an internal circulation of the refrigerant is desired, this circulation being, in contradistinction thereto, external with relatively flat annular members.

Moreover, while the present invention has been described writh respect to a high-power irlystron type tube, it is also understood that it is not limited in its applicability to this type of tube but has general utility for other types of tubes in which interchange of energy takes place between an electron beam and a high frequency electromagnetic wave, particularly in those types of tubes in which velocity modulation occurs.

Thus, it is quite clear that the present invention is not limited to the details shown and described herein but is susceptible of many changes and modifications within the spirit and scope thereof, and I, therefore, do not wish to be limited to the details described and shown herein but intend to cover all such changes and modifications thereof as are encompassed by the scope of the appended claims.

I claim:

1. A high power electron discharge device in which interchange of energy takes place between an electron flow and a high frequency electromagnetic wave within an interaction space having an axis, comprising means for emitting electrons, means within said tube to enable interchange of energy between the electron flow and the electromagnetic wave within said interaction space, means for propagating the electrons emitted by said first mentioned means through said interaction space in an essentially first direction, and collector electrode means for absorbing the electrons emitted by said first mentioned means including means providing electrostatic and magnetic fields to cause movement of the electrons along helicoidal trajectories of increasing diameter on the inside of said collector means and with the axis of at least one of said fields inclined with respect to said first direction.

2. in a high power tube of the velocity modulation type provided with an interaction space in which interchange of energy takes place between an electron flow and a high-frequency electromagnetic wave, an electron collector located at one extremity of the tube and comprising a number of metallic rings, spaced apart and bounding a collector space of increasing diameter start ing from the first ring adjacent said extremity of the tube, said collector space having an axis at an acuate angle with the axis of the interaction space, and all the rings being inclined with respect to the plane containing both the axis of the interaction space and the axis of the collector space, means for applying to said rings electrostatic potentials whose magnitudes decrease starting from said first ring, and means for establishing in said collector space a steady magnetic field substantially parallel to the axis thereof and having decreasing intensities therealong starting from said first ring.

3. In a high power tube of the velocity modulation type provided with an interaction space in which interchange of energy takes place between an electron flow and a high-frequency electromagnetic wave, an electron collector located at one extremity of the tube and com prising a number of metallic rings provided with small paddles inclined with respect to the radii of the rings, said rings being spaced apart and bounding a collector space of increasing diameter starting from the first ring adjacent said extremity of the tube, said collector space havin an axis at an acute angle with the axis of the interaction space, and all the rings being inclined with respect to the plane containing both the axis of the interaction space and the axis of the collector space, means for applying to said rings electrostatic potentials whose magnitudes decrease starting from said first ring, and means for establishing in said collector space a steady magnetic field substantially parallel to the axis thereof and having decreasing intensities therealong starting from said first ring.

4. A high power electron discharge device in which interchange of energy takes place between an electron flow and a high frequency electromagnetic wave, comprising means for producing an electron beam propagating in a predetermined direction, means within said tube effectively constituting an interaction space to enable interchange of energy between the electrons of said beam and the electromagnetic wave, and electrode means for absorbing the electrons emitted by said first mentioned means including means providing a decelerating electrostatic field and a magnetic field of decreasing intensities in said directicn of propagation with the axis of both of said fields inclined with respect to said predetermined direction of propa gation.

5. In a high power tube of the velocity modulation type provided with an interaction space in which interchange of energy takes place between an. electron flow and a high-frequency electromagnetic wave, an electron collector located at one extremity of the tube and comprising a number of metallic rings of different size and a metal plate adjacent the largest ring, said rings being spaced apart and bounding a collector space of increasing diameter starting from the first ring adjacent said extremity of the tube, said collector space having an axis at an acute angle with the axis of the interaction space, and all the rings being inclined with respect to the plane containing both the axis of the interaction space and the axis of the collector space, means for applying to said rings electrostatic potentials whose magnitudes decrease star-ting from said first ring, and means for establishing in said collector space a steady magnetic field substan- '5 tially parallel to the axis thereof and having decreasing intensities therealong starting from said first ring.

6. In a high power tube of the velocity modulation .type provided with an interaction space in which interchange of energy takes place between an electron flow and a high-frequency electromagnetic wave, an electron collector located at one extremity of the tube and comprising a number of metallic rings, spaced apart and bounding a collector space of increasing diameter starting from the first ring adjacent said extremity of the tube and an envelope of insulating material surrounding said rings, said collector space having an axis at an acute angle with the axis of the interaction space, and all the rings being inclined with respect to the plane containing both the axis of the interaction space and the axis of the collector space, means for applying to said rings electrostatic potentials whose magnitudes decrease starting from said first ring, and means for establishing in said collector space a steady magnetic field substantially parallel to the axis thereof and having decreasing intensities therealong starting from said first ring.

7. In a high power tube of the velocity modulation type provided with an interaction space in which interchange of energy takes place between an electron flow and a high-frequency electromagnetic wave, an electron collector located at one extremity of the tube and comprising a number of metallic rings, spaced apart and bounding a collector space of increasing diameter starting from the first ring adjacent said extremity of the tube and an envelope of non-magnetic material surrounding said rings, said collector space having an axis at an acute angle with the axis of the interaction space, and all the rings being incline-d With respect to the plane containing both the axis of the interaction space and the axis of the collector space, means for applying to said rings electrostatic potentials whose magnitudes decrease starting from said first ring, and means for establishing in said collector space a steady magnetic field substantially parallel to the axis thereof and having decreasing intensities there along starting from said first ring.

8. In a high power tube of the velocity modulation type having a tube axis, an electron collector located near one end of the tube and comprising a number of approximately annularly shaped member-s defining therewithin a collector space, said collector space having an axis at an angle with respect to the axis of the tube, means for applying to said members potentials whose magnitudes decrease starting from the first member, and means for establishing in said collector space a magnetic field approximately parallel to the axis thereof and having decreasing intensities thereaiong starting from said first member.

9. In a high power tube of the velocity modulation having an electron how, an electron collector located near one extremity of the tube and comprising a plurality of electron-absorptive members of curved configuration and defining a collector space of increasing cross sectional area in the direction toward said extremity, said collector space being efiectively non-parallel over at least a portion thereof with the electron fiow at the entry thereof into the collector space, means for establishing within said collector space a decelerating electrostatic field in said direction, means for establishing within said collector space a magnetic field having decreasing intensities approximately in said direction, and means including said members for effectively preventing interference in the operation of the tube by either electrons reflected within said collector space or electrons produced by secondary emission from el ctrons impinging on said members.

References Cited in the file of this patent UNITED STATES PATENTS 2,745,983 Dohler et al May 15, 1956 2,916,664 Sternglass Dec. 8, 1959 2,955,225 Sterzer Oct. 4, 1960 2,984,762 Haas May 16, 196 1 

1. A HIGH POWER ELECTRON DISCHARGE DEVICE IN WHICH INTERCHANGE OF ENERGY TAKES PLACE BETWEEN AN ELECTRON FLOW AND A HIGH FREQUENCY ELECTROMAGNETIC WAVE WITHIN AN INTERACTION SPACE HAVING AN AXIS, COMPRISING MEANS FOR EMITTING ELECTRONS, MEANS WITHIN SAID TUBE TO ENABLE INTERCHANGE OF ENERGY BETWEEN THE ELECTRON FLOW AND THE ELECTROMAGNETIC WAVE WITHIN SAID INTERACTION SPACE, MEANS FOR PROPAGATING THE ELECTRONS EMITTED BY SAID FIRST MENTIONED MEANS THROUGH SAID INTERACTION SPACED IN AN ESSENTIALLY FIRST DIRECTION, AND COLLECTOR ELECTRODE MEANS FOR ABSORBING THE ELECTRONS EMITTED BY SAID FIRST MENTIONED MEANS INCLUDING MEANS PROVIDING ELECTROSTATIC AND MAGNETIC FIELDS TO CAUSE MOVEMENT OF THE ELECTRONS ALONG HELICOIDAL TRAJECTORIES OF INCREASING DIAMETER ON THE INSIDE OF SAID COLLECTOR MEANS AND WITH THE AXIS OF AT LEAST ONE OF SAID FIELDS INCLINED WITH RESPECT TO SAID FIRST DIRECTION. 